Tests show no damage to bridge

An early analysis indicates that cracks in Clearwater's Memorial Causeway won't require reconstruction.

By JENNIFER FARRELL
Published February 25, 2004

CLEARWATER - Cracks in the new Memorial Causeway Bridge's four tallest concrete columns aren't bad enough to force crews to tear them down and start over, an early analysis shows.

Preliminary tests ordered by bridge builder PCL Civil Constructors show no obvious evidence of damage to the steel reinforcements that form the spine of the massive concrete support columns, according to PCL's Tampa-based vice president Jerry Harder.

"We're pretty close to setting that aside," Harder said Tuesday.

PCL, the Canadian contractor building the $69.3-million state project, has hired two engineering consultants to study the cracks.

A full report is expected by the end of the week, but Harder said one consultant has recommended injecting epoxy into the biggest cracks, which are roughly 0.02 of an inch. Smaller cracks, at roughly 0.002 of an inch wide, are too tiny to be injected with epoxy, according to Harder. Instead, he said they could be sealed with a surface coating.

The idea is to protect the bridge's steel reinforcements from saltwater intrusion and corrosion. The cracked columns stand on both sides of the main channel in Clearwater Harbor and hold up the highest section of the bridge.

Any fix for the cracks will have to be approved by the state Department of Transportation, which will own the finished bridge. On Tuesday, DOT spokeswoman Marian Scorza said department engineers will wait for proposals from PCL before making a decision on how to proceed.

The cracks were discovered last month after a rainstorm. The hairline cracks are virtually invisible until they get wet, though DOT officials say they would have eventually been discovered during an inspection.

To find out the extent of the damage, engineers for PCL drilled seven cylindrical samples, called "cores," out of the concrete columns. Roughly 4 inches long and 2 inches in diameter, each core was examined for cracks. Engineers took four cores from the column with the most cracks, and one from each of the other three columns, Harder said.

By looking at the size of the cracks and how deeply they penetrate, engineers can determine whether the steel reinforcements inside the columns got bent, said Lawrence Kahn, a civil engineering professor at Georgia Tech contacted by the St. Petersburg Times.

Kahn, who has studied concrete bridges for the past decade, said the smallest of the cracks are common in concrete construction. But the larger cracks need to be filled to prevent corrosion, he said.

Judging by the width of the cracks, it is unlikely the interior steel would have suffered any significant deformity, Kahn said.

John Fisher, a civil engineering professor at Lehigh University in Pennsylvania, also contacted by the Times, agreed.

"We're talking thousandths of an inch," he said. "That's a very small crack."

John Breen, a civil engineering professor at the University of Texas at Austin, said the large cracks are likely repairable, but they merit study.

"That's in the range where you start worrying about durability," Breen said.

"That the concrete is cracked doesn't mean that the structure has failed; it means that it probably has been overstressed," he said. "But (it) quite possibly could be repaired so that it's as good or better than new."

Kahn said PCL's approach to assessing the scope of the problem appears sound. Ideally, though, he said a separate, independent evaluation by FDOT would provide an extra measure of review.

"It just gives a surety of independence," Kahn said. "Even though it almost doubles the cost."

In large jobs such as the Memorial Causeway project, though, experts agreed it is common for contractors to hire their own consultants and propose solutions.

"You have to allow the contractor some breathing room to try and fix the situation," Breen said, adding: "The state is going to have to be convinced. They're going to review what's done."

Harder declined Tuesday to reveal the names of the consultants PCL hired to study the damage.

"There's nothing secret," he said. "We will reveal who they are, but we would prefer to give them the opportunity to finish their work."

Harder said PCL expects to receive another report this week on how to repair another section of the bridge, which fell roughly 7 inches early this month after the scaffolding underneath buckled.